Always start heat-engine service

Do not rely on the notifications to have it started.

https://bugzilla.novell.com/show_bug.cgi?id=859678
Simplify some code that was copied & pasted

The node using the server.rb recipe always has a heat-server role. This
code came from a copy from ceilometer.
Merge pull request #30 from vuntz/bnc859678

Always start heat-engine service
Merge pull request #31 from vuntz/copy-paste

Simplify some code that was copied & pasted